Hydraulic trim/tilt system for outboard propulsion units

ABSTRACT

A hydraulic system for trimming and tilting outboard drives for boats. The system comprises a pump adapted to deliver fluid pressure to a double acting cylinder-piston assembly, which is connected to the tiltable outboard drive unit and to a stationary part of the boat. A valve selects between two modes of operation of the cylinder. In one mode the chambers of the cylinder are interconnected to provide rapid tilt operation. In the other mode, one chamber is connected to the pump and the other is connected to the fluid sump to provide relatively less rapid trimming with greater force.

United States Patent 4 191 Bergstedt 7 i5 1 HYDRAULIC TRIM/TILT SYSTEMFOR OUTBOARD PROPULSION UNITS [75] Inventor: Karl Abdon Bergstedt,Goteborg,

Sweden [73] Assignee: AB Volvo Penta, Goteborg, Sweden [22] Filed: Dec.20, 1972 [2i] Appl. No.: 317,062

[30] Foreign Application Priority Data Dec.2l, 1971 Sweden 16407/71 52us. Cl; 115/41 HT 511 nt. Cl B63h 5/ 2 [5'8] FieldofSearch..'.....115/41 R, 41 HT, 34R,

[56 O i 4 References Cited i UNITED STATES PATENTS 2,451,706 10/1948Aimes ..9l/437 3,008,445 11/1961 Frank .......l15/4 l HT [451 Oct.22,1974- 3,654,889 4/1972 Bergstedt..,.... ll5/4l HT PrimaryExaminerTrygvevM-. Blix Assistant Examiner-Charles E. FrankfortAttorney, Agent, or Firm-George H. Baldwin; Arthur G. Yeager 57 ABSTRACTA hydraulic system fortrimming andv tiltingoutboard drives for boats.The system comprises a pump adapted-to deliver fluid pressure to adouble acting cylinder-piston assembly, which is connected to thetiltable outboard drive unit and ma stationary part of the boatl' Avalve selects between two modes of opera:

tior'i of the cylinder. intone mode thechambers of the cylinder areinterconnected to provide rapid tilt operation. In the other mode, onechamber is connected-to the pump and the other is connected-tothefluidsump to provide relatively less rapid trimming with greaterforce. i e v 8 Claims, 8 Drawing Figures,

HYDRAULIC TRIM/TILT SYSTEM FOR OUTBOARD PROPULSION UNITS Applicantclaims priority based on Swedish application No. 16407/1971 filed Dec.20, 1971.

BACKGROUND OF THE INVENTION In tilting and trimming outboard drives, twomain requirements are to be met. In one case, the tilt movement, whenthe boat lies still and when no propeller thrust acts on the drive, awide range of tilting is to be performed in a short time. Under thiscondition, only a relatively small force is needed. In the second case,the trimming movement, when the boat is driven and the drive issubjected to the propeller thrust, a relatively greater force is neededto achieve the trimming movement. On the other hand the trim angle issmall and a low speed of the trimming movement is desirable to permitaccurate setting of the trim angle.

It is known, for example from US. Pat. No. 3,548,777 Bergstedt, tofulfill the above named requirements by utilizing one hydraulic cylinderwith a relatively small piston area for tilting and a second cylinderwith a relatively large piston area for trimming. By this arrangement itis possible to achieve both the quick tilting movement and the slowtrimming move ment with one pump with constant capacity.

It is, of course, preferred for economy, simplicity and spaceconsiderations to use one, rather than two cylinders for trimming andtilting.

It is an object of the present invention to provide a hydraulic systemwith which it is possible to achieve the above named trimming andtilting functions by using only one cylinder. This is accomplished by avalve unit in the hydraulic system which is adjustable between a firstposition, in which the chamber at the piston rod end of the cylinder isconnected to the chamber at the piston end of the cylinder, and a secondposition, in which the chamber at the piston rod end of the cylinder isconnected to the sump tank.

In the first position of the valve unit, in which it provides a shortcircuit between the two chambers of the cylinder, the fluid pressuredelivered by the pump to the cylinder will act on the difference betweenthe piston areas of the two chambers of the cylinder, i.e., on thecross-sectional area of the piston rod. Since this area is much smallerthan the total piston area exposed to the chamber at the piston end ofthe cylinder, the fluid will cause a fast movement of the piston andlittle force, which is desired during tilting.

It is preferred that the cylinder-piston assembly is arranged, as insaid US. Pat. No. 3,548,777, so that an outward movement of the pistonrod causes an upward tilting of the drive unit.

In the second position of the valve unit the chamber at the piston rodend of the cylinder is drained by a connection to a sump tank. Whenfluid pressure is then dethe first and the second position. In thisembodiment, the manually adjustable valve member is preferablycoordinated to a known locking valve, which is connected to the reversegear of the drive and adapted to lock the connection between the pistonrod side of the cylinder and the tank when shifting from forward toreverse drive.

Such shifting between trim and tilt is achieved, as hereinafter seen,without using any additional control units which should complicate themaneuvring of the boat.

The hydraulic system according to the invention will be fully understoodfrom the following description which refers to the accompanyingdrawings.

FIG. 1 is a side view of an inboard-outboard drive unit for a boatembodying the invention;

FIG. 2 is a schematic view of a previous known hydraulic trim/tiltsystem with two cylinders;

livered to the piston area, it causes a slow motion of the FIG. 3 is aschematic view of a second embodiment of the invention with a manuallyadjustable valve unit;

FIGS. 4a, 4b, 4c and 4d are schematic views of the different positionsof the manually adjustable valve unit; and

FIG. 5 is a schematic side view of the adjusting mechanism for the valveunit in FIGS. 4 a-d.

This invention contemplates an outboard drive unit for a boat, such asthe inboard-outboard unit shown in FIG. 1 as comprising an outboard leg60 mounted for tilting on a pivot 61 to the boat transom 62. The leg isarranged for steering, for example, as shown in US. Pat. No. 3,605,677Bergstedt, and is provided with a cylinder 63 rockably connected to afixed portion 64 of the boat or drive unit and with an extensible pistonrod 36 pivotally connected to the leg, whereby extension of the rodcauses rearward trimming or tilting movement ofthe leg about pivot 61. Acontrol cable or rod linkage 56, 58 leads from a housing 65 which mayform an integral part of the cylinder and in which control valves of thesystem are contained. A pump and fluid pump schematically shown at P isconnected by means of fluid conduits schematically represented at 66 tosupply pressure fluid to and receive return fluid from the controlsystem. A forward, neutral and reverse gear transmission of the unit iscontrolled by lever 67 linked to lever 56.

The known hydraulic system showed in FIG. 2 comprises a reversible pump1 which can deliver fluid in both directions, and it is thereforeconnected to the sump tank 6 over two lines 2 and 3 with back pressurevalves 4 and 5. The pump is also connected to the sump tank via lines 7and 8 comprising safety relief valves 9 and 10. The lines 2 and 3, ofwhich one acts as a suction line and the other as a pressure linedepending on the pump direction of the pump 1, connect the pump to tworegulating valve units 11 and 12, of which the first one 11communicates, via the lines 13 and 14, with the chamber 16 at the pistonend of a double acting tilt cylinder 17 and also with a single actingtrim cylinder 19 in order to regulate the fluid flow to and from thesecylinders. The other regulating valve unit 12 communicates, via the line15, with the chamber 20 at the piston rod end of the double actingcylinder 17. Both valve units 11 and 12 also communicate with the sumptank via respective return lines 21 and 22. Units 11 and 12 compriserespective piston means 25 and 26, which are influenced by the pressurein lines 3 and 2 and which are spring biased by respective compressionsprings 23 and 24 against the pressure in the respective lines. Thepiston means 25 controls the communication between sump return line 21and lines 13 and 14 depending on the pressure in line 3, while pistonmeans 26 controls the communication between sump return line 22 and linedepending on the pressure in line 2.

The hydraulic system further comprises a lock valve 27, which ismanually adjustable and is interposed in the line 15 which communicateswith the chamber in cylinder 17. The system also comprises a safetyrelief valve 29 in a short circuit line 28 connecting between lines 12and 15.

Another safety relief valve is disposed in a channel in the piston 32,said channel connecting chambers 16 and 20 of the double acting cylinderto each other.

Finally, the system also comprises a line 33, which via a relief valve48 connects line 13 to the sump tank.

The described system suffers of very little, actually neglectable,leakage and keeps the pistons 32 and 34 of the cylinders 17 and 19 intheir adjusted positions. The hydraulic cylinders are adapted to actbetween a stationary part of the boat and the tiltable part of the driveunit in such a way that an outward movement of the respective pistonrods 35 and 36 causes an upward swinging movement of the drive. Thisarrangement, being well known in the art, is therefore not further shownin the drawings.

When the angular position of the drive unit is to be adjusted, forupward or downward tilting or trimming, the pump is actuated andconnected in the desired direction until the desired position of thedrive unit is achieved.

When the drive unit is to be tilted from drive position when the boat islying still or is not being driven forward, the function of the systemis as follows:

The pump is actuated and connected in a direction which makes the line 3constitute a suction line and the line 2 a pressure line. The pressurein line 2 opens a spring biased back pressure ball valve 37 in theregulating valve unit 11, whereupon the fluid under pressure isdelivered to chambers 16 and 18 in the cylinders 17 and 19 via lines 13and 14.

Simultaneously, the pressure in line 2 causes the piston 26 in theregulating valve unit 12 to move to the right as seen in FIG. 2 and thusto force open a back pressure valve 38 in the valve unit 12, whereuponchamber 20 in the cylinder 17 communicates with the sump tank 6 via theline 15 and the return line 22. The trimming cylinder has a relativelyshort stroke. As the piston 32 of the cylinder 17 has a smaller areathan the piston 34 of cylinder 19 and as the same pressure prevails inthe cylinder chambers 16 and 18, a fast outward movement of the pistonrod 35, and thus a fast tilting of the drive, is achieved after thepiston 34 has reached its limit. As seen in U.S. Pat. No. 3,548,777, therod 36 is so arranged that the outboard leg swings away therefrom beyondthe trim range.

For downward tilting of the drive the pump is actuated in the oppositedirection, so that line 3 constitutes a pressure line and line 2 asuction line. It will be apparent that the direction of rotation of thepump may be reversed to provide pressure to line 3 and to draw fluidfrom line 2 or that merely the input and output connections to the pumpmay be reversed to provide this result without reversing the actualdirection of rotation of the pump itself. Via a spring biased backpressure valve 39 in the regulating valve unit 12 fluid is delivered tochamber 20 in the cylinder 17. Simultaneously, the pressure in line 3causes piston 25 in the valve unit 11 to open a spring biased backpressure valve in the valve unit 11, whereupon the cylinder chambers 16and 18 communicate with the tank 6 via the line 13, the back pressurevalve 40 and the return line 21. In this case an inward movement of thepiston 32 and finally of both pistons 32 and 34 and a downward movementof the drive are achieved.

When the boat is propelled, whereby the piston rods 35 and 36 areexposed to the force caused by the propeller thrust which tends to pressthe pistons inwardly, the cylinder 17, due to its small piston area, isnot able to produce an outwardly directed force which is enough toovercome the propeller force and accomplish a short movement of thedrive for trimming. At trimming, whereby the fluid flow corresponds tothe above described one for tilting, the short movement of the drive isinstead accomplished primarily by the cylinder 19 with the piston 34which has a larger piston area, assisted to some extent by the lesserforce of piston 32.

It shall be mentioned in this connection that the cylinder 19 ispreferable positioned so that a relatively long moment arm is obtained,which is made possible by the fact that only a relatively short swingingmotion is needed for trimming compared with tilting. The cylinder 17,however, is positioned so that a relatively short moment arm isobtained, in order to get a fast and wide swinging movement.

Of the other valves 27, 29 and 30 which are comprised in the hydraulicsystem, the valve 27 works as a lock valve which is manually adjustabletogether with the gear mechanism of the drive in order to block thedrainage from the cylinder chamber 20. In this way it is ensured thatthe drive will not be tilted by the rearwardly directed propeller forceduring reverse drive. The valve 29 is a safety release valve whichpermits drainage of the chamber 20 if the drive is exposed to an extremerearwardly directed force, for example upon impact with a submerged orfloating object. Valve 30 has the same function when the lock valve 27is in its locking position.

The hydraulic system according to the invention will hereafter bedescribed with reference to FIGS. 3, 4a, 4b, 4c, 4d, and 5 in which thecomponents corresponding to those in FIG. 2 have been given the samenumbers as in FIG. 2. The system showed in FIG. 3 connects at fluidlines 13, 15 and 33 to the system as shown in FIG. 2. The differencebetween the system according to this invention as shown in FIG. 3 andthe prior art system of FIG. 2 lies, as will be seen, in the omission ofcylinder 19, in the substitution of valve 50 for valve 27, and in theprovision of short circuit line 52. Furthermore, since in the FIG. 2system, the cylinder 17 performs the tilting function and the functionof preventing tilting movement of the outboard leg during operation inreverse gear, whereas cylinder 63 according to the invention performsthese functions as well as the function of trimming the leg duringforward driving of the boat, the cylinder 63 should be of largerdimensions, for a drive unit of the same power, than are required forthe cylinder 17. In other respects, cylinder 63 may be identical tocylinder 17 as above described, being provided with a throughpistonsafety valve 30 for the purposes hereinabove explained.

In accord with the system of FIG. 2, line 13 is pressurized when thepump is actuated to trim or tilt the outboard leg, while a sump returnconnection is opened to line 15. When the pump is actuated in thereverse direction (or with reversed connections), line 15 is pressurizedand line 13 is opened to a sump return line. When the pump is notactuated, lines 13 and 15 are blocked off although, as described, thesafety valves 48, 29 and 30 are provided to prevent excessive build-upof destructive pressures therein.

According to the invention, the manually actuated valve 50 controls orprovides not only the reverse lock function (ascribed to valve 27 of thesystem of FIG. 2) but also control and selection of the trimming andtilting operations.

The valve 50 comprises a rotatably movable valve member 51, which isconnected or coupled to the reverse gear control mechanism of the driveover a lost motion mechanism (FIG. 5) so that shifting of the gears ofthe drive unit between forward, reverse and neutral also causes anadjustment of the valve member 51. The lost motion" mechanism is in theshown embodiment constituted by a control lever 56 with slots 55 inwhich pins 57 on the valve member 51 mesh. The slots are dimensioned sothat a 30 lost motion of the control lever is provided before the member51 is engaged. The control lever is connected to the reverse gearcontrol mechanism via a push-pull rod 58 or the like.

By using a lost motion mechanism two positions of the valve member 51are achieved in the neutral position of the drive gear and the controllever 56, namely: a first neutral position is achieved by shifting gearsfrom forward drive to neutral, and a second neutral position is achievedby shifting gears from reverse drive to neutral. The different positionsof the valve member 51 are shown in FIGS. 4a 4d. In the position shownin FIG. 4a the chamber 20 of cylinder 63 communicates with the sump tank6 via achannel 53 in the valve member 51 and via line 15. The drive gearcontrol is in position for forward drive. The system is now adjusted fortrimming. Upon actuation of pump 1 in one direction, the outboard leg isslowly and forceably trimmed aft, or upon such actuation in the oppositedirection, it is slowly trimmed forwardly. In FIG. 4b there is shownsaid first neutral position which is obtained by a 60 clockwiseadjustment of the control lever 56 from the position in which the drivegears are engaged for forward drive into the position in which the gearsare in neutral. This position of lever 56 is that shown in solid linesin FIG. 5. The lost motion between the lever and the valve member 51 is30. The valve member is thus adjusted 30 but is still maintainingcommunciation between the chamber 20 and the sump tank and the system,consequently, is still in position for trimming as shown in FIG. 4b.Upon a further 60 clockwise adjustment of said lever to position thegears for reverse drive, the valve member 51 is adjusted 60 and blocksthe drainage from chamber 20 as FIG. 40 shows. This corresponds to theearlier described locking position in which the drive is held downwithout being influenced by the backwardly directed propeller force.Upon a 60 readjustment in a counterclockwise direction of the controllever from reverse gear position to the position in which the gears areplaced in neutral, a 30 adjustment of the valve member 51 is obtained tosaid second neutral position. In this position, as is shown in FIGS.

3, 4d and 5, the valve establishes communication between chambers 16 and20 of the cylinder 63 via a channel 54, the channel 53 and the shortcircuit line 52. This constitutes a tilting connection for the cylinder,and if, now, the pump is actuated in the tilting direction, theeffective piston area is the cross sectional area of the rod 35.Finally, a further adjustment of the gear control linkage into theforward drive gear posi tion, with the accompanying 60 movement of thelever 56, returns the valve element 51 into the position shown in FIG.4a.

In operation, boats are more frequently operated in forward gear, andonly occasionally in reverse gear. So long as the gear shift linkage isshifted between forward drive and neutral, the trimming and tiltingsystem remains in condition for trimming, with the valve element movingbetween its positions of FIGS. 4a and 4b. If the gears are thrown intoreverse, the valve member moves into reverse lock position, FIG. 40, toprevent kicking up of the outboard leg 60. In order to tilt the legrapidly, the linkage is shifted into reverse gear position and thenreturned to neutral, valve member 51 then being in its FIGS. 3, 4d and 5position and lever 56 in the solid line position of FIG. 5. If the lever56 is not first moved into the reverse gear position and then intoneutral, tilting can be accomplished with the valve member in either ofits trimming positions of FIG. 4a or FIG. 4b, though at a much slowerrate than with the valve member in its FIG. 4d position.

U.S. Patents having some pertinence in connection with the presentinvention include No. 3,003,724 Kiekhaefer; No. 3,434,448 Woodfill; No.3,653,270 Bergstedt; and No. 3,581,702 Moberg, in addition to No.3,548,777 identified above.

While the invention has been described with respect to certain specificembodiments, it will be appreciated that many modifications and changesmay be made by those skilled in the art without departing from thespirit of the invention. It is intended, therefore, by the appendedclaims to cover all such modifications and changes as fall within thetrue spirit and scope of the invention.

What is claimed as new and what it is desired to se-.

cure by Letters Patent of the United States is:

' 1. A hydraulic system for trimming and tilting of outboard driveunitsfor boats, comprising pump means adapted to deliver hydraulicliquid from a liquid sump to a double acting cylinder-piston assembly,said cylinder-piston assembly being arranged between said tiltable driveunit and the boat or a stationary part of the drive, characterized by avalve unit, said valve unit being adjustable between a first positionand a second position and comprising means for connecting said pumpmeans to the chamber at the piston rod end of the cylinder and to thechamber at the piston end of the cylinder when said valve unit is insaid first position to tilt said drive unit and for disconnecting saidchamber at said piston rod end of said cylinder from said chamber at thepiston end of said cylinder and for connecting said chamber at saidpiston rod end of said cylinder with said sump when said valve unit isin said second,

position to trim said drive unit, and manual control means for adjustingsaid valve unit between its said positions.

2. In a hydraulic system for trimming and tilting an outboard drive legfor boats about a horizontal tilt axis comprising a hydraulic liquidsump, a double acting hydraulic cylinder-piston assembly including apiston rod and having a cylinder with a piston therein dividing thespace in the cylinder into a first chamber at the piston end and asecond chamber at the piston rod end of said cylinder, means connectingsaid cylinder and rod between said leg and said boat and spanning saidaxis, and a reversible pressure liquid pump connected to said firstchamber, valve means connected to said sump and to each of said chambersadjustable between a first and a second position and comprising meansfor connecting said second chamber to said first chamber when in saidfirst position to tilt said drive leg and for connecting said secondchamber to said sump when in said second position to trim said driveleg, and manual control means for adjusting said valve means between itssaid two positions.

3. In a drive unit for a boat including a hydraulic system for trimmingand tilting an outboard drive leg about a horizontal tilt axis, saidsystem comprising a hydraulic liquid sump, a double acting hydrauliccylinderpiston assembly including a piston rod and having a cylinderwith a piston therein dividing the space in the cylinder into a firstchamber at the piston end and a second chamber at the piston rod end ofsaid cylinder, means connecting said cylinder and rod between said legand said boat and spanning said axis, and a source of pressure liquidconnected to said first chamber, said unit comprising a forward, neutraland reverse gear transmission and manually movable means for shiftingsaid gears, said system being characterized by including valve meansconnected to said sump and to each of said chambers adjustable between afirst and a second position and comprising means for connecting saidsecond chamber to said first chamber when in said first position to tiltsaid drive leg and for connecting said second chamber to said sump whenin said second position to trim said drive leg, and means coupling saidvalve means to said manually movable means for coordinate adjustmentthereof between said positions in response to gear shifting movement ofsaid manual means.

4. The combination according to claim 3, characterized in that saidvalve means is further adjustable into a third position into which it isadjusted in response to movement of said manually movable means into theposition to shift said gear transmission into reverse, and said valvemeans further comprises means for closing off said second chamber whenin said third position.

5. The combination according to claim 3 wherein said means coupling saidvalve means to said manually movable means includes a lost motionconnection.

6. The combination according to claim 3 wherein said means connectingsaid valve means to said manually movable means includes a lost motionconnection, and wherein, upon movement of said manually movable means toshift said transmission gears from reverse into neutral, said valvemeans is thereby adjusted into its said first position, and, uponfurther movement of said manually movable means to shift saidtransmission gears from neutral into forward gear, said valve means isadjusted thereby into its said second position, said lost motionconnection being operative, upon return movement of said manuallymovable means from its forward gear position to shift said transmissiongears into neutral, to render said connecting means inoperative toreturn said valve means into its said first position.

7. The combination according to claim 6, characterized in that saidvalve means is further adjustable into a third position into which it isadjusted in response to movement of said manually movable means into theposition to shift said gear transmission into reverse, and said valvemeans further comprises means for closing off said second chamber whenin said third position.

8. In a drive unit for a boat including a hydraulic system for trimmingand tilting an outboard drive leg about a horizontal tilt axis, saidsystem comprising a hydraulic fluid sump, a double acting hydrauliccylinderpiston assembly including a piston rod and having a cylinderwith a piston therein dividing the space in the cylinder into a firstchamber at the piston end and a second chamber at the piston rod end ofsaid cylinder, means connecting said cylinder and rod between said legand said boat and spanning said axis, and a selectively operablepressure fluid pump means connected to said first chamber, said unitcomprising a forward, neutral and reverse gear transmission and manuallymovable gear shift means for shifting said gears between forward,neutral and reverse, said system being characterized by including valvemeans connected to said sump and to each of said chambers adjustablebetween first, second, third and fourth positions, said valve meanscomprising means to open hydraulic connection between said secondchamber and said first chamber when in said first position, to openhydraulic connection between said second chamber and said sump in saidsecond and third positions, and closing off hydraulic connection to saidsecond chamber in said fourth position, means coupling said valve meansto said manually movable means for adjustment thereof coordinate withmovement of said manually movable means and operable to adjust saidvalve means into said first position in response to movement of saidmanually movable means to shift gears from reverse to neutral, to adjustsaid valve means into said second position in response to movement ofsaid manually movable means to shift gears from neutral into forward, toadjust said valve means into said third position in'response to movementof said manually movable means to shift gears from forward to neutral,and to adjust said valve means into said fourth position in response tomovement of said manually movable means to shift gears from neutral intoreverse, said lost motion means being effective, upon said movement ofsaid manually movable means to shift gears from forward into neutral, tonot adjust said valve means from said third to said first position and,upon said movement to shift gears from reverse into neutral, to notadjust said valve means from said first to said third position.

1. A hydraulic system for trimming and tilting of outboard drive unitsfor boats, comprising pump means adapted to deliver hydraulic liquidfrom a liquid sump to a double acting cylinderpiston assembly, saidcylinder-piston assembly being arranged between said tiltable drive unitand the boat or a stationary part of the drive, characterized by a valveunit, said valve unit being adjustable between a first position and asecond position and comprising means for connecting said pump means tothe chamber at the piston rod end of the cylinder and to the chamber atthe piston end of the cylinder when said valve unit is in said firstposition to tilt said drive unit and for disconnecting said chamber atsaid piston rod end of said cylinder from said chamber at the piston endof said cylinder and for connecting said chamber at said piston rod endof said cylinder with said sump when said valve unit is in said secondposition to trim said drive unit, and manual control means for adjustingsaid valve unit between its said positions.
 2. In a hydraulic system fortrimming and tilting an outboard drive leg for boats about a horizontaltilt axis comprising a hydraulic liquid sump, a double acting hydrauliccylinder-piston assembly including a piston rod and having a cylinderwith a piston therein dividing the space in the cylinder into a firstchamber at the piston end and a second chamber at the piston rod end ofsaid cylinder, means connecting said cylinder and rod between said legand said boat and spanning said axis, and a reversible pressure liquidpump connected to said first chamber, valve means connected to said sumpand to each of said chambers adjustable between a first and a secondposition and comprising means for connecting said second chamber to saidfirst chamber when in said first position to tilt said drive leg and forconnecting said second chamber to said sump when in said second positionto trim said drive leg, and manual control means for adjusting saidvalve means between its said two positions.
 3. In a drive unit for aboat including a hydraulic system for trimming and tilting an outboarddrive leg about a horizontal tilt axis, said system comprising ahydraulic liquid sump, a double acting hydraulic cylinder-pistonassembly including a piston rod and having a cylinder with a pistontherein dividing the space in the cylinder into a first chamber at thepiston end and a second chamber at the piston rod end of said cylinder,means connecting said cylinder and rod between said leg and said boatand spanning said axis, and a source of pressure liquid connected tosaid first chamber, said unit comprising a forward, neutral and reversegear transmission and manually movable means for shifting said gears,said system being characterized by including valve means connected tosaid sump and to each of said chambers adjustable between a first and asecond position and comprising means for connecting said second chamberto said first chamber when in said first position to tilt said drive legand for connecting said second chamBer to said sump when in said secondposition to trim said drive leg, and means coupling said valve means tosaid manually movable means for coordinate adjustment thereof betweensaid positions in response to gear shifting movement of said manualmeans.
 4. The combination according to claim 3, characterized in thatsaid valve means is further adjustable into a third position into whichit is adjusted in response to movement of said manually movable meansinto the position to shift said gear transmission into reverse, and saidvalve means further comprises means for closing off said second chamberwhen in said third position.
 5. The combination according to claim 3wherein said means coupling said valve means to said manually movablemeans includes a lost motion connection.
 6. The combination according toclaim 3 wherein said means connecting said valve means to said manuallymovable means includes a lost motion connection, and wherein, uponmovement of said manually movable means to shift said transmission gearsfrom reverse into neutral, said valve means is thereby adjusted into itssaid first position, and, upon further movement of said manually movablemeans to shift said transmission gears from neutral into forward gear,said valve means is adjusted thereby into its said second position, saidlost motion connection being operative, upon return movement of saidmanually movable means from its forward gear position to shift saidtransmission gears into neutral, to render said connecting meansinoperative to return said valve means into its said first position. 7.The combination according to claim 6, characterized in that said valvemeans is further adjustable into a third position into which it isadjusted in response to movement of said manually movable means into theposition to shift said gear transmission into reverse, and said valvemeans further comprises means for closing off said second chamber whenin said third position.
 8. In a drive unit for a boat including ahydraulic system for trimming and tilting an outboard drive leg about ahorizontal tilt axis, said system comprising a hydraulic fluid sump, adouble acting hydraulic cylinder-piston assembly including a piston rodand having a cylinder with a piston therein dividing the space in thecylinder into a first chamber at the piston end and a second chamber atthe piston rod end of said cylinder, means connecting said cylinder androd between said leg and said boat and spanning said axis, and aselectively operable pressure fluid pump means connected to said firstchamber, said unit comprising a forward, neutral and reverse geartransmission and manually movable gear shift means for shifting saidgears between forward, neutral and reverse, said system beingcharacterized by including valve means connected to said sump and toeach of said chambers adjustable between first, second, third and fourthpositions, said valve means comprising means to open hydraulicconnection between said second chamber and said first chamber when insaid first position, to open hydraulic connection between said secondchamber and said sump in said second and third positions, and closingoff hydraulic connection to said second chamber in said fourth position,means coupling said valve means to said manually movable means foradjustment thereof coordinate with movement of said manually movablemeans and operable to adjust said valve means into said first positionin response to movement of said manually movable means to shift gearsfrom reverse to neutral, to adjust said valve means into said secondposition in response to movement of said manually movable means to shiftgears from neutral into forward, to adjust said valve means into saidthird position in response to movement of said manually movable means toshift gears from forward to neutral, and to adjust said valve means intosaid fourth position in response to movement of said manually movablemeans to shift gears from neutral into reverse, said lost motion meanSbeing effective, upon said movement of said manually movable means toshift gears from forward into neutral, to not adjust said valve meansfrom said third to said first position and, upon said movement to shiftgears from reverse into neutral, to not adjust said valve means fromsaid first to said third position.